Foch returned from London on 18 March. The first of the five German offensives in 1918 on the Western Front, operation michael (see Map 13), began three days later. The stunning German successes of the opening days supplied, at last, the opportunity for the creation of an Allied unified command.

Operation michael had been long in the planning. Ludendorff knew that a decision had to be reached as to the war’s outcome before the Americans began arriving in great numbers. His general aim was to punch a hole through the front, and to roll up the BEF against the sea. He seems, however, to have wavered over the precise objectives for the three armies devoted to michael. The offensive covered a 103-kilometre-wide front between the rivers Scarpe (at Arras) and Oise (the junction of British and French armies). Impressive staff work assembled the troops of those three armies with their reserves, positioned 6608 guns, and succeeded in fooling the Allies as to the exact area to be attacked. The artillery expert, Colonel Georg Bruchmüller, had drawn up a bigger version of the fire direction schemes that had proved so successful in Riga; and 125 squadrons of aircraft were hidden well away from enemy reconnaissance. The attack divisions (Angriffsdivisionen) had trained and been rested well away from the front, and they were supplemented with specialist units (communications, engineering, medical and so on).